288 USTILAGINKAE. 



Ust. perennans liostr.^ This smut or dust-brand occurs 

 frequently in the Howers of Arrheiiafhcnmi clatius (Fig. 157). 

 The mycelium perennates in the rhizome. 



An Ustilago nearly allied 

 to the preceding one occurs 

 also on Fcdnca prateiisis, 

 Lolium 'prrennc, and other 

 grasses. 



The Smut of Barley. 

 There are really two species 

 of Ustilago found on barley, 



¥ui. \i>^.— Ustilago perennans. Spore-culture Tj„f 7,,.,.,/,,; .,,-,,] JT^f ^,,i,]r, 



in plum-gelatine, (v. Tubeuf del.) ^ ^''- I^-OUIU ,inU Uhl. nUUa. 



Ust. hordei (I'ers.) {Ust. 

 Jrmcni Itostr.) (Britain and U..S. America). This has black 

 spherical spores (6*5 to 7"5ya in diameter), which germinate 

 and give off conidia from a promycelium. The spikelets gene- 

 rally remain enclosed in their coverings. Treatment of seed- 

 corn with a half per cent, copper steep is a certain remedy. 



Ust. nuda (Jens.) (U.S. America). In ears diseased by this 

 smut the epidermis of the glumes is early lost, so that the 

 spore-powder lies freely exposed when the ears emerge from 

 the leaf-sheath. The spores on germination give off' a four- 

 celled promycelium, which however produces no conidia, but 

 develops directly to a septate mycelium. The spores are 

 smooth-coated and oval (5-7/>t long and 5-6'5yU broad); they 

 are matured and set free at the flowering season of the barley, 

 and probably infect seedlings in spring. The spores of this 

 smut are very resistant against treatment with copper steeps, 

 and it is recommended to soften the barley for several hours 

 in cold water before applying Jenson's method. 



Ust. tritici (Pers.) (Britain and U.S. America). Wheat-brand. 

 The spores are developed in the ovary of the wheat, and are 

 black with a tinge of olive-green. On germination they im- 

 mediately form a non-septate mycelium (Fig. 160). 



Heniiing '^ has described spore-cushioiis on tlie leaves and leaf-.slieaths of 

 Triticum vulgare in Upper Egypt. 



Ust. buUata Berk, on Triticum orientale in Turkestan. 



^ Rostrup, Udilaijineae Dauiae, 1890. 

 -Heuning, Zeitschrift f. Fflanzenkraiilcheiten, 1S94. 



